1. Field of Invention
The present invention relates to the field of forehearth concentrates for use in opalescent glass compositions. In particular, the present invention provides a new and improved opalescent forehearth concentrate comprising a non-smelted agglomerated interspersion for forming opalescent glass in the forehearth of a glass furnace, and a method of using the opalescent concentrate. The invention further provides a novel glass composition for use in forming the opalescent concentrate or for use directly in a forehearth.
2. Description of Related Art
Prior art methods of opalization of glass have required high concentrations of opalescent pigment, e.g., greater than 10% to as much as 20% of the overall glass composition, as well as low temperatures and long furnace cycle times to allow striking (nucleation) of the opalescent crystalline additives.
The manufacture of opalescent glass in a forehearth furnace by the addition of either: (i) an opalescent enriched glass frit, or (ii) an opalescent forehearth concentrate comprising a non-smelted compacted interspersion, to a molten clear or colorless base glass is well known. In such processes, the opalescent enriched glass frit or opalescent forehearth concentrate is added to the molten glass flowing through the forehearth of a furnace. This process makes possible the manufacture of both one or more opalescent glass items and clear/colorless glass items from a single melting furnace equipped with multiple forehearths. In the forehearth opalization process, the glass frit or opalescent forehearth concentrate is metered into the molten base glass after the base glass flows from the refining zone or distributor of the furnace and into the forehearth.
Opalescent forehearth concentrates are commonly used in many applications instead of opalescent glass frits because in many applications opalescent concentrates can provide better dispersion of the desired opalescent and avoid the formation of unwanted inclusions and specks in the final opalescent glass product.